Source

File: wp-includes/widgets/class-wp-widget-recent-posts.php

public function __construct() {
		$widget_ops = array(
			'classname'                   => 'widget_recent_entries',
			'description'                 => __( 'Your site’s most recent Posts.' ),
			'customize_selective_refresh' => true,
		);
		parent::__construct( 'recent-posts', __( 'Recent Posts' ), $widget_ops );
		$this->alt_option_name = 'widget_recent_entries';
	}